This all started as a " thought experiment " last summer while looking at the clouds of bats that were hanging out in my backyard. Everyone tries to take BIF's (birds in flight) photos but I wanted to try for BIF's = Bats in flight.

The rest was just some experimentation finding the best settings, since everything has to be set for manual, to get "a shot in the dark"

Actually, it's never completely dark when the bats are the thickest, so I stand at the east edge of my yard facing west, to see their silhouettes in the last of the twilight.